The proper goal is robustness. It is either achieved via clear indication of failure and guidance on alternative solutions - so that the user can handle it. Or by actually failing gracefully and handling as many error conditions in an always reasonable way.

Usually letting user handle it is more general as long as the failures are rare enough.

Internal correctness is perfectly achievable though. External (correct spec) is not.

There are always some unhandled conditions, due to hardware or external component failures...